On Tue, 27 Nov 2012, Daniel Mack wrote: > > OK, this time I got some real results. I can still get the USB packet > > stream to misbehave, and indeed the synthesized data is being lost. > > The output data present on the USB bus smoothly increments during > > each packet, continuing smoothly in adjacent packets. But, when one > > or two packets are missed, the next output data is numbered as if the > > packets (6 stereo frames each) had been generated but lost.
That's how isochronous transfers are supposed to behave. When data is lost, it does not get retransmitted. > > And, what should I look at next? > > As Clemens said, check the error fields in the isochronous frames when > the urb is given back to the driver. For isochronous data, there's > nothing the driver can do about failed transmissions, hence there's no > code to handle such conditions. But it might help understand what's > going on. There probably won't be any errors, but it's worth looking anyway. You never know... > In any case, this now certainly looks more like a strange USB problem, > rather than a bug in snd-usb. The only thing that's strange is that there are so many dropped packets and that they seem to fall into a small number of patterns. This strongly suggests hardware issues. Daniel G., have you tried running your tests on a different computer? Preferably with a different brand of motherboard? Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
